To recover a hydrocarbon resource from a subterranean formation, wellbore casings or pipes are typically coupled together in end-to-end relation within the subterranean formation. The wellbore casings are generally rigid and often times made of steel. In order to more efficiently recover a hydrocarbon resource from the subterranean formation, it may be desirable to apply radio frequency (RF) power to the subterranean formation within (or adjacent to) the hydrocarbon resource.
For example, U.S. Pat. No. 8,616,273 to Trautman, et al. and U.S. Pat. No. 8,960,291 to Parsche, which are both assigned to Harris Corporation of Melbourne, Fla., the assignee of the present application, disclose a method of heating a petroleum ore by applying RF energy to a mixture of petroleum ore.
U.S. Patent Application Publication Nos. 2010/0218940 (now U.S. Pat. No. 8,887,810 B2 issue on Nov. 18, 2014), 2010/0219108 (now U.S. Pat. No. 8,133,384 B2 issue on Mar. 13, 2012), 2010/0219184 (now U.S. Pat. No. 8,729,440 B2 issue on May 20, 2014), 2010/0223011 (now U.S. Pat. No. 8,494,775 B2 issue on Jul. 23, 2013), 2010/0219182 (now U.S. Pat. No. 8,674,274 B2 issue on Mar. 18, 2014), also all to Parsche, and all of which are assigned to the assignee of the present application, disclose apparatuses for heating a hydrocarbon resource by RF energy. U.S. Patent Application Publication No. 2010/0219105 (now U.S. Pat. No. 8,128,786 B2 issue on Mar. 6, 2012) to White et al., assigned to the assignee of the present application, discloses a device for RF heating to reduce use of supplemental water added in the recovery of unconventional oil.
As an example of improvements to RF transmission lines, U.S. Pat. No. 8,847,711 to Wright et al., assigned to the assignee of the present application, discloses a series of rigid coaxial sections coupled together in end-to-end relation for use in hydrocarbon resource recovery. Each rigid coaxial section includes an inner conductor and a rigid outer conductor surrounding the inner conductor. Each of the rigid outer conductors includes a rigid outer layer having opposing threaded ends defining overlapping mechanical threaded joints with adjacent rigid outer layers.
U.S. Pat. No. 8,960,272 to Wright et al., also assigned to the assignee of the present application, discloses an RF apparatus for hydrocarbon resource recovery that includes a series of tubular conductors. Each of the tubular conductors may have threads at opposing ends. In addition, the RF apparatus may include bendable tubular dielectric couplers that rotationally interlock opposing ends of the tubular conductors to define a tubular antenna.
To apply the RF energy to the hydrocarbon resource, a rigid coaxial feed arrangement or RF transmission line may be desired to couple to an antenna in the subterranean formation. Typical commercial designs of a rigid coaxial feed arrangement are not generally designed for structural loading or subterranean use, as installation generally requires long runs of the transmission line along the lines of 500-1500 meters. In addition, the transmission line is subjected to significant compressive and tensile loads from thermal expansion and the physical weight of the components of the transmission line.
As an example, a typical overhead transmission line may be capable of 1,000 lbs tension, while it may be desirable for a downhole RF transmission line to have 150,000 to 500,000 lbs tensile capability, which may amount to 150 to 500 times the capacity of an existing commercial product.
In addition, the commercial rigid coaxial designs may be bulky, and require multiple nuts, bolts, washers, and other fasteners to hold the coaxial sections together. Further, larger diameter coaxial sections may limit subterranean uses and a lower profile increases high voltage margins, while reducing antennae bore diameter and wellbore size requirements.
Further improvements to hydrocarbon resource recovery and RF transmission lines may be desirable. For example, it may be desirable to increase the efficiency of assembling a high strength RF transmission line that can withstand relatively high stresses associated with hydrocarbon resource recovery in a subterranean formation.